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Integrated resilience assessment of bridges and transport networks exposed to hydraulic hazards

Periodic Reporting for period 1 - ReBounce (Integrated resilience assessment of bridges and transport networks exposed to hydraulic hazards)

Reporting period: 2020-09-01 to 2022-08-31

Bridges are key assets of transport networks. Hydraulic actions, especially scour are the leading causes of their failure worldwide. Exacerbated by climate change, bridge failures induce fatalities and traffic disruptions with severe economic and societal consequences. To date, the lack of fragility functions and recovery models has prevented the development of a reliable framework for risk and resilience assessment of bridges exposed to hydraulic hazards. As a result, network operators are unable to prioritise restoration and allocate resources objectively and systematically. The goal of ReBounce is to fill this important capability gap by delivering a reliable framework for the quantification of risk and resilience of flood-critical bridges and the associated transport networks upon which they reside. To this end, the project will deliver: (i) realistic and sufficient flood intensity measures for representative bridge typologies; (ii) rigorous vulnerability models; (iii) novel multi-parameter restoration functions that will simulate the effect of restoration tasks on the capacity and functionality of bridges accounting for uncertainties in the idle times and resourcefulness; (iv) test-application of the developed assessment framework on two different road networks (case studies).
The action will be carried out by Dr Marianna Loli (Fellow), under the supervision of Prof. Dr Stergios Mitoulis, University of Surrey (UoS). Research objectives include:
R1. Definition of realistic and sufficient flood Intensity Measures (IM) for bridge typologies found in Europe.
R2. Delivery of novel adaptive fragility models.
R3 Development of original multi-parameter restoration functions.
R4. Application of the proposed framework for assessing the resilience of critical case study networks.
In addition to the research tasks, ReBounce aims to provide cutting-edge training to the Fellow through attendance of courses, secondments and short visits to global academic institutions and industry leaders, and collaboration with interdisciplinary research groups. The project activities will foster widespread communication of outputs through publications, media outreach, and through the organization of an exploitation workshop targeted to
To achieve the first research objective (R1), an ensemble of new flood hazard indicators appropriate for the evaluation of the hydraulic impact on bridges was developed, and validated, based on a systematic analysis of the response of actual structures during severe flooding and a comparison between inspected data and analytical predictions. The results of this task showed that the use of the proposed bridge-specific flood intensity measures is key for a reliable assessment of hazard intensity and the associated risk of failure.
A large number of numerical simulations were carried out and thoroughly validated against inspected field responses. This led to the development of a simple yet reliable bridge vulnerability model (research objective R2) which can be used for the assessment of any stream-crossing bridge based on engineering parameters that are easy to measure or deduce, such as the construction age, the type of the foundation and the width and shape of the piers.
In addition to damage prediction (vulnerability), the assessment of resilience necessitates the prediction of post-hazard response (i.e. the temporal evolution of reinstatement). This is possible through the use of restoration models. The models that were developed in this project (research objective R3) can be used to analytically represent the reinstatement and capacity restoration of scour-damaged bridges, to estimate the duration of restoration tasks and the duration of functionality reinstatement for reference bridge typologies. They were produced based on the statistical processing of responses to an expert elicitation survey and validated against a documented case study.
Integration of a comprehensive, bridge-specific scheme for the analysis of flood hazard with a rapid, operationally feasible, scheme for the assessment of vulnerability, and a broad, socio-economic framework for the evaluation of consequences (Fig.1) led to the development of a semi-quantitative flood risk assessment methodology, which was then implemented for the analysis of two case-study networks:
(i) The road network of the municipality of Karditsa in Central Greece, which was impacted by a Mediterranean hurricane in September 2020. This task included archival research and GIS analysis of a total of 117 bridge structures of diverse engineering properties, and varying vulnerability and significance for the network.
(ii) The road network of the Greater Maputo Area, in Mozambique. Here the risk assessment considered socioeconomic criteria to take into account the increased vulnerability of residents living in extreme poverty as well as that of vulnerable groups, namely children and hospitalized people.

Dissemination of project outputs to the scientific community, academic groups and research centres working on relevant areas and the industry was pursued through:
1) Publications: 5 journal publications and 3 articles in international conferences have been produced, reporting outputs of the project.
2) Presentations in conferences: A total of 6 presentations in 6 international conferences and multi-stakeholder dissemination events.
3) Exploitation Workshop: A very successful workshop was organized by the Fellow to take place in the framework of the International Conference on Natural Hazards and Infrastructure (ICONHIC 2022).
ReBounce has proposed a thorough, albeit technically and operationally feasible, flood risk assessment framework appropriate for the analysis of river-crossing bridges, intended as a tool that will assist transport network operators not only in the identification of flood-critical bridge assets but in the prioritization of flood adaptation interventions for the minimization of consequences. This framework enables the strategic prioritization of proactive and reactive climate adaptation measures for critical transport infrastructure, therefore incentivising a more resilient way of managing infrastructure.
The developed methodology fills a capability gap in the existing literature on flood hazard indexing in that it integrates the flow velocity, in addition to floodwater height, as a critical, representative intensity parameter, appropriate for the analysis of problems where failure is dominated by flow–structure interaction. Thereby, it captures the sensitivity of bridge structures to the multitude of adverse mechanisms that lead to bridge damage during flooding.
An extensive validation study has been performed employing a large number of field observations relevant to the response of different types of bridges to a severe flood. The results confirm the reliability of the method demonstrating that the framework is a crucial step towards the accurate prediction of bridge damages within risk-based assessment guidelines.
The proposed framework is a tool to guide the adaptation of the transport sector to the impacts of climate change. As such, the outcomes of this project respond to urgent safety and socio-economic needs of the EU in alignment with the strategic priorities of Horizon 2020 as well as the UN Sustainable Development Goal 9 to “build resilient infrastructure, promote sustainable industrialization and foster innovation”.